Vehicle in-wheel drive motor and a body side drive motor

ABSTRACT

A vehicle drive device uses in-wheel motors to drive a vehicle and includes in-wheel motors that are provided in wheels of a vehicle and drive the wheels, a body side motor that is provided in a body of the vehicle and drives the wheels, and a controller that controls the in-wheel motors and the body side motor based on requested output power of a driver, in which the controller causes the body side motor to generate a driving force and the in-wheel motors not to generate driving forces when the requested output power of the driver is less than predetermined output power and the controller causes the body side motor and the in-wheel motors to generate driving forces when the requested output power of the driver is equal to or more than the predetermined output power.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on PCT filing PCT/JP2019/011427, filedMar. 19, 2019, which claims priority to JP 2018-052636, filed Mar. 20,2018, and JP 2018-143353, filed Jul. 31, 2018, the entire contents ofeach are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a vehicle drive device and, moreparticularly, to a vehicle drive device that uses in-wheel motors todrive a vehicle.

BACKGROUND ART

In recent years, exhaust gas regulations for vehicles have been enhancedand demands for fuel efficiency and carbon dioxide emissions per traveldistance for vehicles have become strict in various countries in theworld. In addition, some cities regulate entry of vehicles traveling byan internal combustion engine into urban areas. To satisfy theserequests, hybrid-drive vehicles having an internal combustion engine andmotors and electric vehicles driven only by motors have been developedand widely used.

Japanese Patent No. 5280961 (PTL 1) describes a drive control device forvehicles. In this drive control device, a drive device is provided onthe rear wheel side of the vehicle and two motors provided in this drivedevice drive the rear wheels of the vehicle, respectively. In additionto this drive device, a drive unit formed by connecting an internalcombustion engine and a motor that are in series is provided in thefront portion of the vehicle. The power of the drive unit is transmittedto the front wheels via the transmission and the main drive shaft andthe power of the drive device is transmitted to the rear wheels of thevehicle. In addition, in this drive control device, the two motors ofthe drive device are driven when the vehicle starts, and these drivingforces are transmitted to the rear wheels of the vehicle, respectively.In addition, the driving unit also generates a driving force duringacceleration of the vehicle and the four-wheel drive is achieved by thedriving unit and the two motors of the drive device. As described above,in the drive control device described in PTL 1, the two motors providedmainly for the rear wheels of the vehicle generate the driving forces.

CITATION LIST Patent Literature

PTL 1: Japanese Patent No. 5280961

SUMMARY OF INVENTION Technical Problem

Since the driving of a vehicle by motors does not emit carbon dioxideduring a travel, emission regulations that are enhanced each year can beadvantageously satisfied, but it is difficult to ensure a sufficientlylong distance travel because the electric power that can be stored inthe battery is limited. Accordingly, a hybrid drive device having aninternal combustion engine together with motors is widely used as adrive device for vehicles. In addition, even in such a hybrid drivedevice, in order to reduce carbon dioxide emissions during a travel,vehicles that mainly utilize the driving forces of motors like thevehicle described in PTL 1 are increasing.

Such a hybrid drive device driven mainly by the driving forces of motorsas described above needs to have a large capacity battery to obtainsufficient travel performance. In addition, in order to obtain asufficient driving forces by motors, the motors need to be operated at arelatively high voltage. Accordingly, in a hybrid drive device drivenmainly by the driving forces of motors, since a large capacity batteryis necessary and the electrical system that supplies a high voltage tothe motors needs to be electrically insulated sufficiently, the overallweight of the vehicle increases and the fuel efficiency of the vehiclereduces. Furthermore, in order to drive the vehicle with a heavy weightby the motors, a larger capacity battery and a higher voltage arerequired, thereby causing a vicious cycle that further increases theweight.

In addition, in the drive control device of the vehicle described in PTL1, the motors that drive the rear wheels are directly connected to thedrive shafts of the rear wheels, but the motors may be built into therear wheels to form so-called in-wheel motors. Since the drive shaftsthat couple the motors and the wheels are not required when usingin-wheel motors, it is advantageous in that the weight of the driveshafts can be reduced. However, even when the in-wheel motors areadopted as the motors for startup, acceleration, and cruise travel ofthe vehicle as in the invention described in PTL 1, an increase inweight cannot be avoided because large motors are required to obtainsufficient travel performance. Accordingly, the advantage of usingin-wheel motors cannot be obtained sufficiently.

Accordingly, an object of the present invention is to provide a vehicledrive device capable of efficiently driving a vehicle by using in-wheelmotors without falling into the vicious cycle between enhancement ofdriving by motors and an increase in vehicle weight.

Solution to Problem

To solve the problem described above, according to the presentinvention, there is provided a vehicle drive device that uses anin-wheel motor to drive a vehicle, the vehicle drive device including anin-wheel motor that is provided in a wheel of the vehicle and drives thewheel; a body side motor that is provided in a body of the vehicle anddrives the wheel; and a controller that controls the in-wheel motor andthe body side motor based on requested output power of a driver, inwhich the controller causes the body side motor to generate a drivingforce and the in-wheel motor not to generate a driving force when therequested output power of the driver is less than predetermined outputpower, and the controller causes the body side motor and the in-wheelmotor to generate driving forces when the requested output power of thedriver is equal to or more than the predetermined output power.

In the present invention configured as described above, the controllercontrols the in-wheel motor that is provided in the wheel and drives thewheel based on the requested output power of the driver. In addition,when the requested output power of the driver is less than thepredetermined output power, the controller causes the body side motor togenerate a driving force and the in-wheel motor not to generate adriving force. Furthermore, when the requested output power of thedriver is equal to or more than the predetermined output power, thecontroller causes the body side motor and the in-wheel motor to generatedriving forces.

Accordingly, in the present invention, since the body side motor and thein-wheel motor generate driving forces when the requested output powerof the driver is equal to or more than the predetermined output power,the in-wheel motor is not requested for large output power. As a result,since a small motor with small output power may be adopted as thein-wheel motor, the vehicle can be efficiently driven using the in-wheelmotor.

In the present invention, preferably, the vehicle drive device furtherincludes an accelerator position sensor that detects an amount ofdepression of an accelerator pedal of the vehicle, in which thecontroller sets the requested output power of the driver based on theamount of depression of the accelerator pedal detected by theaccelerator position sensor, and the requested output power of thedriver when the amount of depression of the accelerator pedal is largeis set larger than the requested output power of the driver when theamount of depression of the accelerator pedal is small.

In the present invention configured as described above, since therequested output power of the driver is set to a large value when theamount of depression of the accelerator pedal is large, the intention ofthe driver can be more accurately reflected in the requested outputpower.

In the present invention, preferably, the in-wheel motor directly drivesthe wheel in which the in-wheel motor is provided without interventionof a deceleration mechanism.

In the present invention, since the in-wheel motor and the body sidemotor generate driving forces when the requested output power is equalto or more than the predetermined output power, the in-wheel motor isnot requested for a large torque in the low speed range. Accordingly,the in-wheel motor can generate a sufficient torque in the rotationrange in which the torque is requested without providing thedeceleration mechanism. In addition, in the present invention configuredas described above, since the wheel is directly driven withoutintervention of the deceleration mechanism, the deceleration mechanismwith very heavy weight can be omitted and the output loss due to therotation resistance of the deceleration mechanism can be avoided.

In the present invention, preferably, the in-wheel motor is an inductionmotor.

Generally, an induction motor can obtain a large output torque in thehigh rotation range and the weight thereof can be reduced. Accordingly,by adopting an induction motor as the in-wheel motor that is notrequested for a large torque in the low rotation range in the presentinvention, the weight of a motor capable of generating a sufficienttorque in the required rotation range can be reduced.

In the present invention, preferably, the body side motor is a permanentmagnet motor.

Generally, a permanent magnet motor has a relatively large startingtorque and can obtain a large torque in the low rotation range.Accordingly, by adopting a permanent magnet motor as the body side motorthat is requested for a large torque in the low rotation range in thepresent invention, the weight of a motor capable of generating asufficient torque in the required rotation range can be reduced.

In the present invention, preferably, the wheel driven by the in-wheelmotor is a front wheel of the vehicle and the wheel driven by the bodyside motor is a rear wheel of the vehicle.

In the present invention, preferably, the wheel driven by the in-wheelmotor is a rear wheel of the vehicle and the wheel driven by the bodyside motor is a front wheel of the vehicle.

In the present invention, preferably, the wheel driven by the in-wheelmotor and the body side motor is a front wheel of the vehicle.

In the present invention, preferably, the wheel driven by the in-wheelmotor and the body side motor is a rear wheel of the vehicle.

Advantageous Effects of Invention

The hybrid drive device according to the present invention canefficiently drive a vehicle using an in-wheel motor without causing thevicious cycle between enhancement of driving by a motor and an increasein vehicle weight.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a first embodiment of the present invention isinstalled.

FIG. 2 is a perspective view, as seen from above, illustrating a frontportion of the vehicle in which the hybrid drive device according to thefirst embodiment of the present invention is installed.

FIG. 3 is a perspective view, as seen from the side, illustrating thefront portion of the vehicle in which the hybrid drive device accordingto the first embodiment of the present invention is installed.

FIG. 4 is a sectional view taken along line iv-iv in FIG. 2 ,

FIG. 5 is a block diagram illustrating the inputs and outputs of varioussignals in the hybrid drive device according to the first embodiment ofthe present invention.

FIG. 6 is a block diagram illustrating the power supply structure of thehybrid drive device according to the first embodiment of the presentinvention.

FIG. 7 is a diagram schematically illustrating one example of changes involtages when electric power is regenerated into a capacitor in thehybrid drive device according to the first embodiment of the presentinvention.

FIG. 8 is a diagram illustrating the relationship between the outputpower and the vehicle speed of individual motors used in the hybriddrive device according to the first embodiment of the present invention.

FIG. 9 is a sectional view schematically illustrating the structure ofan auxiliary drive motor adopted in the hybrid drive device according tothe first embodiment of the present invention.

FIG. 10 is a flowchart illustrating control by a control device of thehybrid drive device according to the first embodiment of the presentinvention.

FIG. 11 is a graph illustrating examples of operations in individualmodes of the hybrid drive device according to the first embodiment ofthe present invention.

FIG. 12 is a diagram schematically illustrating changes in theacceleration acting on the vehicle when a transmission downshifts orupshifts in the hybrid drive device according to the first embodiment ofthe present invention.

FIG. 13 is a flowchart illustrating control by a control device of ahybrid drive device according to a second embodiment of the presentinvention.

FIG. 14 is a graph illustrating examples of operations in individualmodes of the hybrid drive device according to the second embodiment ofthe present invention.

FIG. 15 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a first modification of the present inventionis installed.

FIG. 16 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a second modification of the present inventionis installed.

FIG. 17 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a third modification of the present inventionis installed.

DESCRIPTION OF EMBODIMENTS

Next, preferred embodiments of the present invention will be describedwith reference to the attached drawings.

FIG. 1 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a first embodiment of the present invention isinstalled. FIG. 2 is a perspective view, as seen from the side,illustrating the front portion of a vehicle in which the hybrid drivedevice according to the embodiment is installed and FIG. 3 is aperspective view, as seen from the side, illustrating the front portionof the vehicle. FIG. 4 is a sectional view taken along line iv-iv inFIG. 2 .

As illustrated in FIG. 1 , a vehicle 1 having the hybrid drive system,which is a vehicle drive device according to the first embodiment of thepresent invention, is a so-called FR (front engine rear drive) vehiclein which an engine 12 as an internal combustion engine is installed inthe front portion (in front of the driver's seat) of the vehicle and apair of left and right rear wheels 2 a as main drive wheels is driven.In addition, as described later, the rear wheels 2 a are also driven bythe main drive motor, which is the main drive electric motor, and a pairof left and right front wheels 2 b which are auxiliary drive wheels, isdriven by the auxiliary drive motors, which are the auxiliary driveelectric motors.

A hybrid drive device 10 according to the first embodiment of thepresent invention installed in the vehicle 1 includes the engine 12 thatdrives the rear wheels 2 a, a power transmission mechanism 14 thattransmits a driving force to the rear wheels 2 a, a main drive motor 16that drives the rear wheels 2 a, a battery 18 that is an electricstorage unit, auxiliary drive motors 20 that drive the front wheels 2 b,a capacitor 22, and a control device 24 that is a controller.

The engine 12 is an internal combustion engine for generating a drivingforce for the rear wheels 2 a, which are the main drive wheels of thevehicle 1. As illustrated in FIGS. 2 to 4 , in the embodiment, anin-line 4-cylinder engine is adopted as the engine 12 and the engine 12disposed in the front portion of the vehicle 1 drives the rear wheels 2a via the power transmission mechanism 14. In addition, as illustratedin FIG. 4 , in the embodiment, the engine 12 is a flywheel-less enginethat does not include a flywheel and installed on a subframe 4 a of thevehicle 1 via engine mounts 6 a. Furthermore, the sub-frame 4 a isfastened and fixed to the lower portions of front side frames 4 b andthe lower portion of a dash panel 4 c at the rear ends thereof.

The power transmission mechanism 14 is configured to transmit thedriving force generated by the engine 12 to the rear wheels 2 a, whichare the main drive wheels. As illustrated in FIG. 1 to FIG. 3 , thepower transmission mechanism 14 includes a propeller shaft 14 aconnected to the engine 12, a clutch 14 b, and a transmission 14 c,which is a stepped transmission. The propeller shaft 14 a extends fromthe engine 12 disposed in the front portion of the vehicle 1 toward therear of the vehicle 1 in a propeller shaft tunnel 4 d (FIG. 2 ). Therear end of the propeller shaft 14 a is connected to the transmission 14c via the clutch 14 b. The output shaft of the transmission 14 c isconnected to the axle shaft (not illustrated) of the rear wheels 2 a anddrives the rear wheels 2 a.

In the embodiment, the transmission 14 c is provided in so-calledtransaxle arrangement. As a result, since the main body of thetransmission with a large outer diameter is not present immediatelybehind the engine 12, the width of the floor tunnel (propeller shafttunnel 4 d) can be reduced, the foot space in the middle of the occupantcan be obtained, and the lower body of the occupant can take asymmetrical posture that faces directly the front. Furthermore, theouter diameter and the length of the main drive motor 16 can easily havesufficient sizes according to the output power thereof while keepingthis posture of the occupant.

The main drive motor 16 is an electric motor for generating a drivingforce for the main drive wheels, provided on the body of the vehicle 1,disposed behind the engine 12 adjacently to the engine 12, and functionsas a body side motor. In addition, an inverter (INV) 16 a is disposedadjacently to the main drive motor 16 and the inverter 16 a converts thecurrent from the battery 18 into alternating current and supplies thealternating current to the main drive motor 16. Furthermore, asillustrated in FIG. 2 and FIG. 3 , the main drive motor 16 is connectedin series to the engine 12 and the driving force generated by the maindrive motor 16 is also transmitted to the rear wheels 2 a via the powertransmission mechanism 14. Alternatively, the present invention may beconfigured so that the driving force is transmitted to the rear wheels 2a via a part of the power transmission mechanism 14 by connecting themain drive motor 16 to an intermediate point of the power transmissionmechanism 14. In addition, the embodiment adopts, as the main drivemotor 16, a 25 kW permanent magnet motor (permanent magnet synchronousmotor) driven by 48 V.

The battery 18 is an electric storage unit that stores electric powerfor mainly operating the main drive motor 16. In addition, asillustrated in FIG. 2 , the battery 18 is disposed inside the propellershaft tunnel 4 d so as to surround the torque tube 14 d that covers thepropeller shaft 14 a in the embodiment. Furthermore, in the embodiment,a 48 V 3.5 kWh lithium ion battery (LIB) is used as the battery 18.

Since the transaxle arrangement is adopted in the embodiment asdescribed above, the volume for accommodating the battery 18 can beexpanded toward the space in front of the floor tunnel (propeller shafttunnel 4 d) created by this arrangement. This can obtain and expand thecapacity of the battery 18 without reducing the space in the middle ofthe occupant by increasing the width of the floor tunnel.

As illustrated in FIG. 4 , the auxiliary drive motors 20 are provided inthe front wheels 2 b under the springs of the vehicle 1 so as togenerate driving forces for the front wheels 2 b, which are theauxiliary drive wheels. In the embodiment, the front wheel 2 b issupported by a double wishbone type suspension and is suspended by anupper arm 8 a, a lower arm 8 b, a spring 8 c, and a shock absorber 8 d.The auxiliary drive motors 20 are in-wheel motors and are housed in thewheels of the front wheels 2 b. Accordingly, the auxiliary drive motors20 are provided in the so-called “under-spring portions” of the vehicle1 so as to drive the front wheels 2 b. In addition, as illustrated inFIG. 1 , the current from the capacitor (CAP) 22 is converted intoalternating current by inverters 20 a and supplied to the auxiliarydrive motors 20. Furthermore, in the embodiment, the auxiliary drivemotors 20 are not provided with deceleration machines that aredeceleration mechanisms, the driving forces of the auxiliary drivemotors 20 are directly transmitted to the front wheels 2 b, and thewheels are directly driven. In addition, in the embodiment, 17 kWinduction motors are adopted as the auxiliary drive motors 20.

The capacitor (CAP) 22 is provided so as to store the electric powerregenerated by the auxiliary drive motors 20. As illustrated in FIG. 2and FIG. 3 , the capacitor 22 is disposed immediately in front of theengine 12 and supplies electric power to the auxiliary drive motors 20provided in the front wheels 2 b of the vehicle 1. As illustrated inFIG. 4 , in the capacitor 22, brackets 22 a projecting from both sidesurfaces thereof are supported by the front side frames 4 b via acapacitor mount 6 b. In addition, a harness 22 b extending from theauxiliary drive motor 20 to the capacitor 22 passes through the upperend of the side wall of the wheel house and is led to the engine room.In addition, the capacitor 22 is configured to store electric charge ata voltage higher than in the battery 18 and is disposed in a regionbetween the left and right front wheels 2 b, which are the auxiliarydrive wheels. The auxiliary drive motors 20, which are driven mainly bythe electric power stored in the capacitor 22, are driven by a voltagehigher than in the main drive motor 16.

The control device 24 controls the engine 12, the main drive motor 16,and the auxiliary drive motors 20 to execute a motor travel mode and aninternal combustion engine travel mode. Specifically, the control device24 can include a microprocessor, a memory, an interface circuit, aprogram for operating these components (these components are notillustrated), and the like. Details on control by the control device 24will be described later.

In addition, as illustrated in FIG. 1 , a high voltage DC/DC converter26 a and a low voltage DC/DC converter 26 b, which are voltageconverting units, are disposed near the capacitor 22. The high voltageDC/DC converter 26 a, the low voltage DC/DC converter 26 b, thecapacitor 22, and the two inverters 20 a are unitized to form anintegrated unit.

Next, the overall structure, the power supply structure, and the drivingof the vehicle 1 by the individual motors in the hybrid drive device 10according to the first embodiment of the present invention will bedescribed with reference to FIG. 5 to FIG. 8 .

FIG. 5 is a block diagram illustrating the inputs and outputs of varioussignals in the hybrid drive device 10 according to the first embodimentof the present invention. FIG. 6 is a block diagram illustrating thepower supply structure of the hybrid drive device 10 according to thefirst embodiment of the present invention. FIG. 7 is a diagramschematically illustrating one example of changes in voltages whenelectric power is regenerated into the capacitor 22 in the hybrid drivedevice 10 according to the embodiment. FIG. 8 is a diagram illustratingthe relationship between the output power of the motors used in thehybrid drive device 10 according to the embodiment and the vehiclespeed.

First, the inputs and outputs of various signals in the hybrid drivedevice 10 according to the first embodiment of the present inventionwill be described. As illustrated in FIG. 5 , the control device 24receives the detection signals detected by a mode selection switch 40, avehicle speed sensor 42, an accelerator position sensor 44, a brakesensor 46, an engine RPM sensor 48, an automatic transmission (AT) inputrotation sensor 50, an automatic transmission (AT) output rotationsensor 52, a voltage sensor 54, and a current sensor 56. In addition,the control device 24 controls the inverter 16 a for the main drivemotor, the inverters 20 a for the auxiliary drive motors 20, the highvoltage DC/DC converter 26 a, the low voltage DC/DC converter 26 b, afuel injection valve 58, a spark plug 60, and a hydraulic solenoid valve62 of the transmission 14 c by control signals to these components.

Next, the power supply structure of the hybrid drive device 10 accordingto the first embodiment of the present invention will be described. Asillustrated in FIG. 6 , the battery 18 and capacitor 22 included in thehybrid drive device 10 are connected in series to each other. The maindrive motor 16 is driven by approximately 48 V, which is the referenceoutput voltage of the battery 18, and the auxiliary drive motors 20 aredriven by a maximum voltage of 120 V, which is higher than the sum ofthe output voltage of the battery 18 and the inter-terminal voltage ofthe capacitor 22. Therefore, the auxiliary drive motors 20 are alwaysdriven by the electric power supplied via the capacitor 22.

In addition, the inverter 16 a is mounted to the main drive motor 16 andconverts the output of the battery 18 into alternating current throughwhich the main drive motor 16, which is a permanent magnet motor, isdriven. Similarly, the inverters 20 a are mounted to the auxiliary drivemotors 20 and convert the outputs of the battery 18 and the capacitor 22into alternating current through which the auxiliary drive motors 20,which are induction motors, are driven. Since the auxiliary drive motors20 are driven by a voltage higher than in the main drive motor 16, theharness (electric wires) 22 b that supplies electric power to theauxiliary drive motors 20 needs to have high insulation. However, sincethe capacitor 22 is disposed close to the auxiliary drive motors 20, anincrease in the weight due to high insulation of the harnesses 22 b canbe minimized.

Furthermore, when, for example, the vehicle 1 decelerates, the maindrive motor 16 and the auxiliary drive motors 20 function as generatorsand generate electric power by regenerating the kinetic energy of thevehicle 1. The electric power regenerated by the main drive motor 16 isstored in the battery 18 and the electric power regenerated by theauxiliary drive motors 20 is stored mainly in the capacitor 22.

In addition, the high voltage DC/DC converter 26 a, which is a voltageconverting unit, is connected between the battery 18 and the capacitor22 and this high voltage DC/DC converter 26 a charges the capacitor 22by raising the voltage of the battery 1 g when the electric chargestored in the capacitor 22 is insufficient (when the inter-terminalvoltage of the capacitor 22 drops). In contrast, when the inter-terminalvoltage of the capacitor 22 rises to a predetermined voltage or higherdue to regeneration of energy by the auxiliary drive motors 20, thebattery 18 is charged by reducing the electric charge stored in thecapacitor 22 and applying the electric charge to the battery 18. Thatis, the electric power regenerated by the auxiliary drive motors 20 isstored in the capacitor 22, and then the battery 18 is charged with apart of the stored electric charge via the high voltage DC/DC converter26 a.

Furthermore, the low voltage DC/DC converter 26 b is connected betweenthe battery 18 and 12V electric components 25 of the vehicle 1. Sincemany of the control device 24 of the hybrid drive device 10 and theelectric components 25 of the vehicle 1 operate at a voltage of 12V, thevoltage of the electric charge stored in the battery 18 is reduced to12V by the low voltage DC/DC converter 26 b and supplied to thesedevices.

Next, charging and discharging of the capacitor 22 will be describedwith reference to FIG. 7 .

As illustrated in FIG. 7 , the voltage of the capacitor 22 is the sum ofthe base voltage of the battery 18 and the inter-terminal voltage of thecapacitor 22 itself. When, for example, the vehicle 1 decelerates, theauxiliary drive motors 20 regenerate electric power and the capacitor 22is charged with the regenerated electric power. When the capacitor 22 ischarged, the inter-terminal voltage rises relatively rapidly. When theinter-terminal voltage of the capacitor 22 rises to a predeterminedvoltage or more due to the charging, the voltage of the capacitor 22 isreduced by the high voltage DC/DC converter 26 a and the battery 18 ischarged. As illustrated in FIG. 7 , the charging to the battery 18 fromthe capacitor 22 is performed relatively slowly than the charging to thecapacitor 22 and the voltage of the capacitor 22 drops to a propervoltage relatively slowly.

That is, the electric power regenerated by the auxiliary drive motors 20is temporarily stored in the capacitor 22 and then the battery 18 isslowly charged with the regenerated electric power. Depending on thetime when the regeneration is performed, the regeneration of electricpower by the auxiliary drive motors 20 may overlap with the chargingfrom the capacitor 22 to the battery 18.

In contrast, the battery 18 is directly charged with the electric powerregenerated by the main drive motor 16.

Next, the relationship between the vehicle speed and the output power ofthe motors in the hybrid drive device 10 according to the firstembodiment of the present invention will be described with reference toFIG. 8 . FIG. 8 is a graph illustrating the relationship between thespeed of the vehicle 1 and the output power of the motors in the hybriddrive device 10 according to the embodiment. In FIG. 8 , the outputpower of the main drive motor 16 is represented by a dotted line, theoutput power of one of the auxiliary drive motors 20 is represented by adot-dash line, the sum of the output power of the two auxiliary drivemotors 20 is represented by a dot-dot-dash line, and the sum of theoutput power of all motors is represented by a solid line. Although FIG.8 illustrates the speed of the vehicle 1 on the horizontal axis and theoutput power of the motors on the vertical axis, since there is acertain relationship between the speed of the vehicle 1 and the numberof revolutions of each of the motors, the output power of the motorsdraws curves similar to those in FIG. 8 even when the number ofrevolutions of each of the motors is represented on the horizontal axis.

Since a permanent magnet motor is adopted as the main drive motor 16 inthe embodiment, as represented by the dotted line in FIG. 8 , the outputpower of the main drive motor 16 is large in a low vehicle speed rangein which the number of revolutions of the motor is low and the motoroutput power that can be output reduces as the vehicle speed increases.That is, in the embodiment, the main drive motor 16 is driven byapproximately 48 V, outputs a torque (maximum torque) of approximately200 Nm up to approximately 1000 rpm, and the torque reduces with theincrease in the number of revolutions at approximately 1000 rpm or more.In addition, in the embodiment, the main drive motor 16 is configured toobtain a continuous output power of approximately 20 kW and a maximumoutput power of approximately 25 kW in the lowest low speed range.

In contrast, since induction motors are used as the auxiliary drivemotors 20, the output power of the auxiliary drive motors 20 is verysmall in the low vehicle speed range, the motor outputs increase as thespeed becomes higher, the maximum output power is obtained at a vehiclespeed close to 130 km/h or so, and then the motor output power reduces,as represented by the dot-dash line and the dot-dot-dash line in FIG. 8. In the embodiment, the auxiliary drive motors 20 are driven byapproximately 120 V. and each of them obtains an output power ofapproximately 17 kW and the two motors obtain a total output power ofapproximately 34 kW at a vehicle speed close to 130 km/h or so. That is,in the embodiment, each of the auxiliary drive motors 20 has a peak ofthe torque curve and obtains a maximum torque of approximately 200 Nm atapproximately 600 to 800 rpm.

The solid line in FIG. 8 represents the sum of the output power of themain drive motor 16 and the two auxiliary drive motors 20. As is clearfrom this graph, in the embodiment, a maximum output power ofapproximately 53 kW is obtained at a vehicle speed close to 130 km/h orso and the travel condition requested in the WLTP test at this vehiclespeed is satisfied at this maximum output power. In addition, althoughthe output power values of the two auxiliary drive motors 20 are summedup even in the low vehicle speed range as represented by the solid linein FIG. 8 , the auxiliary drive motors 20 are actually not driven in thelow vehicle speed range as described later. That is, the vehicle isdriven only by the main drive motor 16 at startup and in a low vehiclespeed range and the two auxiliary drive motors 20 generate output poweronly when large output power is required in the high vehicle speed range(for example, when the vehicle 1 is accelerated in the high vehiclespeed range). By using the induction motors (auxiliary drive motors 20)capable of generating large output power in the high rotation range onlyin the high speed range as described above, sufficient output power canbe obtained when necessary (for example, when acceleration at apredetermined speed or more is performed) while an increase in vehicleweight is kept low.

Next, the structure of the auxiliary drive motors 20 adopted in thehybrid drive device 10 according to the first embodiment of the presentinvention will be described with reference to FIG. 9 . FIG. 9 is asectional view schematically illustrating the structure of the auxiliarydrive motor 20.

As illustrated in FIG. 9 , the auxiliary drive motor 20 is an outerrotor type induction motor including a stator 28 and a rotor 30 thatrotates around this stator.

The stator 28 includes a substantially discoid stator base 28 a, astator shaft 28 b extending from the center of the stator base 28 a, anda stator coil 28 c attached around the stator shaft 28 b. In addition,the stator coil 28 c is housed in an electrical insulating liquidchamber 32, immersed in electrical insulating liquid 32 a that fills theelectrical insulating liquid chamber, and subject to boiling cooling viathe liquid.

The rotor 30 is formed in a substantially cylindrical shape so as tosurround the periphery of the stator 28 and has a substantiallycylindrical rotor body 30 a with one end closed and a rotor coil 30 bdisposed on the inner peripheral wall surface of the rotor body 30 a.The rotor coil 30 b is disposed facing the stator coil 28 c so as togenerate induction current by the rotational magnetic field generated bythe stator coil 28 c. In addition, the rotor 30 is supported by abearing 34 attached to the end of the stator shaft 28 b so as to rotatesmoothly around the stator 28.

The stator base 28 a is supported by an upper arm 8 a and a lower arm 8b (FIG. 4 ) that suspend the front wheels of the vehicle 1. In contrast,the rotor body 30 a is directly fixed to the wheels of the front wheels2 b (not illustrated). Alternating current converted by the inverters 20a flows through the stator coil 28 c and generates a rotational magneticfield. This rotational magnetic field causes an induced current to flowthrough the rotor coil 30 b and generates a driving force that rotatesthe rotor body 30 a. As described above, the driving forces generated bythe auxiliary drive motors 20 rotationally drives the wheels of thefront wheels 2 b (not illustrated) directly.

Next, the operation of the motor travel mode and the operation of theinternal combustion engine travel mode performed by the control device24 will be described with reference to FIG. 10 and FIG. 11 . FIG. 10 isa flowchart illustrating control by the control device 24 and FIG. 11 isa graph illustrating examples of the operations of these modes. Theflowchart illustrated in FIG. 10 is repeatedly executed at predeterminedtime intervals while the vehicle 1 operates.

The graph illustrated in FIG. 11 represents, in order from the top, thespeed of the vehicle 1, the torque generated by the engine 12, thetorque generated by the main drive motor 16, the torque generated by theauxiliary drive motors 20, the voltage of the capacitor 22, the currentof the capacitor 22, and the current of the battery 18. In the graphrepresenting the torque of the main drive motor 16 and the torques ofthe auxiliary drive motors 20, positive values mean the state in whichmotors generate torques and negative values mean the state in whichmotors regenerate the kinetic energy of the vehicle 1. In addition, inthe graph representing the current of the capacitor 22 and the currentof the battery 18, negative values mean the state in which electricpower is supplied (discharged) to motors and positive values mean thestate of charging with the electric power regenerated by motors.

First, in step S1 in FIG. 10 , it is determined whether the vehicle 1has been set to the internal combustion engine travel mode (ENG mode).That is, the vehicle 1 has the mode selection switch 40 (FIG. 5 ) thatselects either the internal combustion engine travel mode or the motortravel mode (EV mode) and it is determined in step S1 which mode hasbeen set. Since the motor travel mode is set at time t₁ in FIG. 11 , theprocessing of the flowchart in FIG. 10 proceeds to step S2.

Next, in step S2, it is determined whether the speed of the vehicle 1 isequal to or more than a predetermined vehicle speed. The processingproceeds to step S6 when the speed is equal to or more than thepredetermined vehicle speed or the processing proceeds to step S3 whenthe speed is less than the predetermined vehicle speed. Since the driverhas started the vehicle 1 and the vehicle speed is low at time t₁ inFIG. 11 , the processing of the flowchart proceeds to step S3.

Furthermore, in step S3, it is determined whether the vehicle 1 isdecelerating (whether the brake pedal (not illustrated) of the vehicle 1is being operated). The processing proceeds to step S5 when the vehicle1 is decelerating or the processing proceeds to step S4 when the vehicle1 is accelerating or traveling at a constant speed (when the brakesensor 46 (FIG. 5 ) does not detect the operation of the brake pedal).Since the driver has started the vehicle 1 and is accelerating thevehicle 1 (accelerator position sensor 44 (FIG. 5 ) has detected thatthe accelerator pedal of the vehicle 1 has been operated by apredetermined amount or more) at time t₁ in FIG. 11 , the processing ofthe flowchart proceeds to step S4 and the processing of the flowchart inFIG. 10 is completed once. In step S4, the main drive motor 16 generatesa torque and the vehicle speed increases (from time t₁ to time t₂ inFIG. 11 ). At this time, since discharge current flows from the battery18 that supplies electric power to the main drive motor 16 and dischargecurrent from the capacitor 22 remains zero because the auxiliary drivemotors 20 do not generate torques, the voltage of the capacitor 22 doesnot change. The current and voltage are detected by the voltage sensor54 and the current sensor 56 (FIG. 5 ) and input to the control device24. In addition, from time t₁ to time t₂ in FIG. 11 , the engine 12 isnot driven because the motor travel mode is set. That is, since thecontrol device 24 stops fuel injection via the fuel injection valve 58of the engine 12 and does not perform ignition via the ignition plug 60,the engine 12 does not generate a torque.

In the example illustrated in FIG. 11 , the vehicle 1 accelerates fromtime t₁ to time t₂ and then travels at a constant speed until time t₃.In this period, the processing of steps S1, S2, S3, and S4 in theflowchart in FIG. 10 is repeatedly executed. During this low speedtravel, since the torque generated by the main drive motor 16 becomessmaller than the torque during the acceleration, the current dischargedfrom the battery 18 also becomes smaller.

Next, when the driver operates the brake pedal (not illustrated) of thevehicle 1 at time t₃ in FIG. 11 , the processing of the flowchart inFIG. 10 proceeds to step S5 from step S3. In step S5, the driving by themain drive motor 16 is stopped (no torque is generated) and the kineticenergy of the vehicle 1 is regenerated as electric power by theauxiliary drive motors 20. The vehicle 1 is decelerated by theregeneration of the kinetic energy, the discharge current from battery18 becomes zero, the charge current flows through the capacitor 22because the electric power is regenerated by the auxiliary drive motors20, and the voltage of the capacitor 22 rises.

When the vehicle 1 stops at time t₄ in FIG. 11 , the charge current tothe capacitor 22 becomes zero and the voltage of the capacitor 22 alsobecomes constant. Next, the vehicle 1 is started again at time t₅ andreaches a constant speed travel (time t₆), and the processing of stepsS1, S2, S3, and S4 in the flowchart in FIG. 10 is repeatedly executeduntil the deceleration of the vehicle 1 is started (time t₇). When thedeceleration of the vehicle is started at time t₇, the processing ofsteps S1, S2, S3, and S5 in the flowchart in FIG. 10 is repeatedlyexecuted and the auxiliary drive motors 20 regenerates electric power.As described above, the motor travel mode is set while the vehiclestarts and stops repeatedly at a relatively low speed in urban areas orthe like, the vehicle 1 functions purely as an electric vehicle (EV) andthe engine 12 does not generate a torque.

Furthermore, when the vehicle 1 is started at time t₈ in FIG. 11 , theprocessing of steps S1, S2, S3, and S4 in the flowchart in FIG. 10 isrepeatedly executed and the vehicle 1 is accelerated. Next, when thespeed of the vehicle 1 detected by the vehicle speed sensor 42 (FIG. 5 )exceeds a predetermined first vehicle speed at time t₉, the processingof the flowchart proceeds to step S6 from step S2. In step S6, it isdetermined whether the vehicle 1 is decelerating (the brake pedal isbeing operated). Since the vehicle 1 is not decelerating at time t₉, theprocessing of the flowchart proceeds to step S7. In step S7, it isdetermined whether the vehicle 1 is accelerating by a predeterminedvalue or more (whether the accelerator pedal of the vehicle 1 has beenoperated by a predetermined amount or more). In the embodiment, thepredetermined first vehicle speed is set to approximately 100 km/h,which is more than a travel speed of 0 km/h.

Since the vehicle 1 is accelerating by a predetermined value or more attime t₉ in the example illustrated in FIG. 11 , the processing proceedsto step S8, in which the main drive motor 16 is driven and the auxiliarydrive motors 20 are also driven. When the vehicle 1 is accelerated by apredetermined value or more at the predetermined first vehicle speed ormore at which the motors are requested for high output power in themotor travel mode as described above, electric power is supplied to themain drive motor 16 and the auxiliary drive motors 20 to obtain therequired power, and this drives the vehicle 1. In other words, thecontrol device 24 starts the vehicle 1 (time t₈) by causing the maindrive motor 16 to generate a driving force and then causes the auxiliarydrive motors 20 to generate driving forces when the travel speed of thevehicle 1 detected by the vehicle speed sensor 42 reaches the firstvehicle speed (time t₉). At this time, the battery 18 supplies electricpower to the main drive motor 16 and the capacitor 22 supplies electricpower to the auxiliary drive motors 20. Since the capacitor 22 supplieselectric power as described above, the voltage of the capacitor 22drops. While the vehicle 1 is driven by the main drive motor 16 and theauxiliary drive motors 20 (from time t₉ to time t₁₀), the processing ofsteps S1, S2, S6, S7, and S8 in the flowchart is repeatedly executed.

As described above, the auxiliary drive motors 20 generate drivingforces when the travel speed of the vehicle 1 is equal to or more thanthe predetermined first vehicle speed and are prohibited from generatingdriving forces when the travel speed is less than the first vehiclespeed. Although the first vehicle speed is set to approximately 100 km/hin the embodiment, the first vehicle speed may be set to any vehiclespeed that is equal to or more than approximately 50 km/h according tothe output characteristics of the adopted auxiliary drive motors 20. Incontrast, the main drive motor 16 generates a driving force when thetravel speed of the vehicle 1 is less than a predetermined secondvehicle speed including zero or when the travel speed is equal to ormore than the second vehicle speed. The predetermined second vehiclespeed may be set to a vehicle speed identical to or different from thefirst vehicle speed. In addition, in the embodiment, the main drivemotor 16 always generates a driving force when the driving force isrequested in the motor travel mode.

Next, when the vehicle 1 shifts to a constant speed travel (when theaccelerator pedal is operated by less than a predetermined amount) attime t₁₀ in FIG. 11 , the processing of steps S1, S2, S6, S7, and S9 inthe flowchart is repeatedly executed. In step S9, driving by theauxiliary drive motors 20 is stopped (no torque is generated) and thevehicle 1 is driven only by the main drive motor 16. Even when thevehicle 1 travels at the predetermined vehicle speed or more, thevehicle 1 is driven only by the main drive motor 16 if the accelerationis less than the predetermined amount.

In addition, since the voltage of the capacitor 22 drops to thepredetermined value or less because the capacitor 22 has driven theauxiliary drive motors 20 from time t₉ to time t₁₀, the control device24 sends a signal to the high voltage DC/DC converter 26 a at time t₁₀to charge the capacitor 22. That is, the high voltage DC/DC converter 26a raises the voltage of the electric charge stored in the battery 18 andcharges the capacitor 22. This causes the current for driving the maindrive motor 16 and the current for charging the capacitor 22 to bedischarged from the battery 18 from time t₁₀ to time t₁₁ in FIG. 11 . Iflarge electric power is regenerated by the auxiliary drive motors 20 andthe voltage of the capacitor 22 rises to a predetermined value or more,the control device 24 sends a signal to the high voltage DC/DC converter26 a to reduce the voltage of the capacitor 22 and charges the battery18. As described above, the electric power regenerated by the auxiliarydrive motors 20 is consumed by the auxiliary drive motors 20, or storedin the capacitor 22 and then used to charge the battery 18 via the highvoltage DC/DC converter 26 a.

When the vehicle 1 decelerates (the brake pedal is operated) at time t₁₁in FIG. 11 , the processing of steps S1, S2, S6, and S10 in theflowchart will be repeatedly executed. In step S10, the kinetic energyof the vehicle 1 is regenerated as electric power by both the main drivemotor 16 and the auxiliary drive motors 20. The electric powerregenerated by the main drive motor 16 is stored in the battery 18 andthe electric power regenerated by the auxiliary drive motors 20 isstored in the capacitor 22. As described above, when the brake pedal isoperated at the specified vehicle speed or more, electric power isregenerated by both the main drive motor 16 and the auxiliary drivemotors 20 and electric charge is stored in the capacitor 22 and thebattery 18.

Next, at time t₁₂ in FIG. 11 , the driver switches the mode of thevehicle 1 from the motor travel mode to the internal combustion enginetravel mode by operating the mode selection switch 40 (FIG. 5 ) anddepresses the accelerator pedal (not illustrated). When the mode of thevehicle 1 is switched to the internal combustion engine travel mode, theprocessing of the flowchart in FIG. 10 by the control device 24 proceedsto step S11 from step S1, and the processing of step S11 and subsequentsteps is executed.

First, in step S11, it is determined whether the vehicle 1 stops. Whenthe vehicle 1 does not stop (the vehicle 1 is traveling), it isdetermined in step S2 whether the vehicle 1 is decelerating (whether thebrake pedal (not illustrated) is being operated). Since the vehicle 1 istraveling and the driver is operating the accelerator pedal at time t₁₂in FIG. 11 , the processing of the flowchart in FIG. 10 proceeds to stepS13.

In step S13, the supply of fuel to the engine 12 starts and the engine12 generates a torque. That is, since the output shaft (not illustrated)of the engine 12 is directly connected to the output shaft (notillustrated) of the main drive motor 16 in the embodiment, the outputshaft of the engine 12 always rotates together with driving by the maindrive motor 16. However, the engine 12 does not generate a torque in themotor travel mode because fuel supply to the engine 12 is performed,but, in the internal combustion engine travel mode, the engine 12generates a torque because fuel supply (fuel injection by the fuelinjection valve 58 and ignition by the ignition plug 60) starts.

In addition, immediately after switching from the motor travel mode tothe internal combustion engine travel mode, the control device 24 causesthe main drive motor 16 to generate a torque for starting the engine(from time t₁₂ to time t₁₃ in FIG. 11 ). This torque for starting theengine is generated to cause the vehicle 1 to travel until the engine 12actually generates a torque after fuel supply to the engine 12 isstarted and suppress torque fluctuations before and after the engine 12generates a torque. In addition, in the embodiment, when the number ofrevolutions of the engine 12 at the time of switching to the internalcombustion engine travel mode is less than a predetermined number ofrevolutions, fuel supply to the engine 12 is not started and the fuelsupply is started when the number of revolutions of the engine 12 isequal to or more than the predetermined number of revolutions due to thetorque for starting the engine. In the embodiment, when the number ofrevolutions of the engine 12 detected by the engine RPM sensor 48 risesto 2000 rpm or more, fuel supply is started.

While the vehicle 1 accelerates or travels at a constant speed after theengine 12 is started, the processing of steps S1, S11, S12, and S13 inthe flowchart in FIG. 10 is repeatedly executed (from time t₁₃ to timet₁₄ in FIG. 11 ). As described above, in the internal combustion enginetravel mode, the engine 12 exclusively outputs the power for driving thevehicle 1 and the main drive motor 16 and the auxiliary drive motors 20do not output the power for driving the vehicle 1. Accordingly, thedriver can enjoy the driving feeling of the vehicle 1 driven by theinternal combustion engine.

Next, when the driver operates the brake pedal (not illustrated) at timet₁₄ in FIG. 11 , the processing of the flowchart in FIG. 10 proceeds tostep S14 from step S12. In step S14, fuel supply to the engine 12 isstopped and fuel consumption is suppressed. Furthermore, in step S15,the main drive motor 16 and the auxiliary drive motors 20 regenerate thekinetic energy of the vehicle 1 as electric energy and charge currentflows through the battery 18 and the capacitor 22. As described above,during deceleration of the vehicle 1, the processing of steps S1, S11,S12, S14, and S15 is repeatedly executed (from time t₁₄ to time t₁₅ inFIG. 11 ).

During deceleration of the vehicle 1 in the internal combustion enginetravel mode, the control device 24 performs downshift torque adjustmentby driving the auxiliary drive motors 20 in switching (shifting) of thetransmission 14 c, which is a stepped transmission. The torque generatedby this torque adjustment complements an instantaneous torque drop orthe like and is not equivalent to the torque that drives the vehicle 1.Details on torque adjustment will be described later.

On the other hand, when the vehicle 1 stops at time t₁₅ in FIG. 11 , theprocessing of the flowchart in FIG. 10 proceeds to step S16 from stepS11. In step S16, the control device 24 supplies the minimum fuelrequired to maintain the idling of the engine 12. In addition, thecontrol device 24 generates an assist torque via the main drive motor 16so that the engine 12 can maintain idling at a low number ofrevolutions. As described above, while the vehicle 1 stops, theprocessing of steps S1, S11, and S16 is repeatedly executed (from timet₁₅ to time t₁₆ in FIG. 11 ).

Although the engine 12 is a flywheel-less engine in the embodiment,since the assist torque generated by the main drive motor 16 acts as apseudo flywheel, the engine 12 can maintain smooth idling at a lownumber of revolutions. In addition, adoption of a flywheel-less enginemakes the response of the engine 12 high during a travel in the internalcombustion engine travel mode, thereby enabling driving with a goodfeeling.

In addition, when the vehicle 1 starts from a stop state in the internalcombustion engine travel mode, the control device 24 increases thenumber of revolutions of the main drive motor 16 (the number ofrevolutions of the engine 12) to a predetermined number of revolutionsby sending a signal to the main drive motor 16. After the number ofrevolutions of the engine is increased to the predetermined number ofrevolutions, the control device 24 supplies the engine 12 with fuel fordriving the engine, causes the engine 12 to perform driving, andperforms a travel in the internal combustion engine travel mode.

Next, torque adjustment during switching (shifting) of the transmission14 c will be described with reference to FIG. 12 .

FIG. 12 is a diagram that schematically illustrates changes in theacceleration that acts on the vehicle when transmission 14 c downshiftsor upshifts, and represents, in order from the top, examples ofdownshift torque down, downshift torque assistance, and upshift torqueassistance.

In the internal combustion engine travel mode, the hybrid drive device10 according to the first embodiment of the present invention causes thecontrol device 24 to automatically switch the clutch 14 b and thetransmission 14 c, which is an automatic transmission, according to thevehicle speed and the number of revolutions of the engine when theautomatic shift mode is set. As illustrated in the upper part of FIG. 12, when the transmission 14 c downshifts (shifts to a low speed) withnegative acceleration acting on the vehicle 1 during deceleration (timet₁₀₁ in FIG. 12 ), the control device 24 disconnects the clutch 14 b todisconnect the output shaft of the engine 12 from the main drive wheels(rear wheels 2 a). When the engine 12 is disconnected from the maindrive wheels in this way, since the rotation resistance of the engine 12no longer acts on the main drive wheels, the acceleration acting on thevehicle 1 instantaneously changes to a positive side, as indicated bythe dotted line in the upper part of FIG. 12 . Next, the control device24 sends a control signal to the transmission 14 c and switches thebuilt-in hydraulic solenoid valve 62 (FIG. 5 ) to increase the reductionratio of the transmission 14 c. Furthermore, when the control device 24connects the clutch 14 b at time t₁₀₂ at which the downshift iscompleted, the acceleration changes to a negative side again. Althoughthe period from the start to the completion of a downshift (from timet₁₀₁ to time t₁₀₂) is generally 300 to 1000 msec, the occupant is givenan idle running feeling and may have a discomfort feeling due to aso-called torque shock in which the torque acting on the vehicleinstantaneously changes.

In the hybrid drive device 10 according to the embodiment, the controldevice 24 makes torque adjustment by sending a control signal to theauxiliary drive motors 20 at the time of a downshift to suppress theidle running feeling of the vehicle 1. Specifically, when the controldevice 24 performs a downshift by sending a signal to the clutch 14 band the transmission 14 c, the control device 24 reads the number ofrevolutions of the input shaft and the number of revolutions of theoutput shaft of the transmission 14 c detected by the automatictransmission input rotation sensor 50 and the automatic transmissionoutput rotation sensor 52 (FIG. 5 ), respectively. Furthermore, thecontrol device 24 predicts changes in the acceleration generated in thevehicle 1 based on the number of revolutions of the input shaft and thenumber of revolutions of the output shaft that have been read and causesthe auxiliary drive motors 20 to regenerate energy. This suppresses aninstantaneous rise in the acceleration (change to the positive side) ofthe vehicle 1 due to a torque shock as indicated by the solid line inthe upper part of FIG. 12 , thereby suppressing an idling runningfeeling. Furthermore, in the embodiment, the torque shock in the maindrive wheels (rear wheels 2 a) caused by a downshift is complemented bythe auxiliary drive wheels (front wheels 2 b) via the auxiliary drivemotors 20. Accordingly, torque adjustment can be made without beingaffected by the dynamic characteristics of the power transmissionmechanism 14 that transmits power from the engine 12 to the main drivewheels.

In addition, as indicated by the dotted line in the middle part of FIG.12 , when a downshift is started at time t₁₀₃ with positive accelerationacting on the vehicle 1 during acceleration, the output shaft of theengine 12 is disconnected from the main drive wheels (rear wheels 2 a).Accordingly, since the drive torque by the engine 12 does not act on therear wheels 2 a and a torque shock occurs, the occupant may be given astall feeling by the time the downshift is completed at time t₁₀₄. Thatis, the acceleration of the vehicle 1 instantaneously changes to thenegative side at time t₁₀₃ at which a downshift is started and theacceleration changes to the positive side at time t₁₀₄ at which thedownshift is completed.

In the hybrid drive device 10 according to the embodiment, whenperforming a downshift, the control device 24 predicts changes in theacceleration caused in the vehicle 1 based on detection signals from theautomatic transmission input rotation sensor 50 and the automatictransmission output rotation sensor 52 and causes the auxiliary drivemotors 20 to generate driving forces. As indicated by the solid line inthe middle part of FIG. 12 , this suppresses an instantaneous drop(change to the negative side) of the acceleration of the vehicle 1 by atorque shock and suppresses a stall feeling.

Furthermore, as indicated by the dotted line in the lower part of FIG.12 , when an upshift is started at time t₁₀₅ with positive accelerationacting on the vehicle 1 (positive acceleration reduces with time) duringacceleration, the output shaft of the engine 12 is disconnected from themain drive wheels (rear wheels 2 a). Accordingly, since the drive torqueby the engine 12 does not act on the rear wheels 2 a and a torque shockoccurs, the occupant may be given a stall feeling by the time theupshift is completed at time t₁₀₆. That is, the acceleration of thevehicle 1 instantaneously changes to the negative side at time t₁₀₅ atwhich the upshift is started and the acceleration changes to thepositive side at time t₁₀₆ at which the upshift is completed.

In the embodiment, when performing an upshift, the control device 24predicts changes in the acceleration caused in the vehicle 1 based ondetection signals from the automatic transmission input rotation sensor50 and the automatic transmission output rotation sensor 52 and causesthe auxiliary drive motors 20 to generate driving forces. As indicatedby the solid line in the lower part of FIG. 12 , this suppresses aninstantaneous drop (change to the negative side) of the acceleration ofthe vehicle 1 due to a torque shock and suppresses a stall feeling.

As described above, the adjustment of the drive torque by the auxiliarydrive motors 20 during a downshift or an upshift of the transmission 14c is performed in a very short time and does not substantially drive thevehicle 1. Therefore, the power generated by the auxiliary drive motors20 can be generated by the electric charge regenerated by the auxiliarydrive motors 20 and stored in the capacitor 22. In addition, theadjustment of the drive torque by the auxiliary drive motors 20 can beapplied to an automatic transmission with a torque converter, anautomatic transmission without a torque converter, an automated manualtransmission, and the like.

In the hybrid drive device 10 according to the first embodiment of thepresent invention, since the wheels (front wheels 2 b) are directlydriven by the auxiliary drive motors 20 without intervention of adeceleration mechanism (FIG. 4 and FIG. 9 ), the deceleration mechanismwith very heavy weight can be omitted and the output loss due to therotation resistance of the deceleration mechanism can be avoided.

In addition, in the hybrid drive device 10 according to the embodiment,by adopting induction motors as the in-wheel motors that are theauxiliary drive motors 20 (step S8 in FIG. 10 ) not requested for alarge torque in the low rotation range (FIG. 4 and FIG. 9 ) in which therequested output power of the driver is small, lightweight motorscapable of generating a sufficient torque in the required rotation rangecan be achieved.

In addition, in the hybrid drive device 10 according to the embodiment,by adopting a permanent magnet motor as the main drive motor 16requested for a large torque also in the low rotation range (step S4 inFIG. 10 ) in which the requested output power of the driver is small, alightweight motor capable of generating a sufficient torque in therequired rotation range can be achieved.

Next, a vehicle drive device that is a hybrid drive device according toa second embodiment of the present invention will be described withreference to FIG. 13 and FIG. 14 .

The vehicle drive device according to the embodiment is different fromthat of the first embodiment in the control executed by the controldevice 24. Accordingly, since the structure of the vehicle drive devicedescribed with reference to FIG. 1 to FIG. 9 is the same as that of thefirst embodiment, the description thereof will be omitted and only thepoints of the second embodiment of the present invention that aredifferent from those of the first embodiment will be described here.

FIG. 13 is a flowchart illustrating control by the control deviceinstalled in the vehicle drive device according to the second embodimentof the present invention and FIG. 14 is a graph illustrating one exampleof operation in the motor travel mode. The flowchart illustrated in FIG.13 indicates the processing (corresponding to the processing of step S2and subsequent steps in the flowchart illustrated in FIG. 10 ) executedwhen the mode selection switch 40 of the vehicle 1 is set to the motortravel mode. The processing executed in the engine travel mode of thevehicle control device according to the embodiment is the same as thatof the first embodiment. In addition, the flowchart illustrated in FIG.13 is repeatedly executed at predetermined time intervals while thevehicle 1 operates.

The graph illustrated in FIG. 14 represents, in order from the top, thespeed of the vehicle 1, the output requested for the motors to achievethis target acceleration, the target acceleration of the vehicle 1 thatis set based on a driving operation by the driver, the torque generatedby the engine 12, the torque generated by the main drive motor 16, andthe torque generated by the auxiliary drive motors 20. Since the graphillustrated in FIG. 14 represents the operation in the motor travelmode, the torque generated by the engine 12 is always set to zero. Inaddition, in the graph representing the torque of the main drive motor16 and the torque of the auxiliary drive motors 20, positive values meanthat motors are generating torques and negative values mean that motorsare regenerating the kinetic energy of the vehicle 1.

First, in step S201 in FIG. 13 , detection signals from various sensorsare read. Specifically, detection signals from the vehicle speed sensor42, the accelerator position sensor 44, the brake sensor 46, and thelike are read into the control device 24.

Next, in step S202, the target acceleration is set based on thedetection signals from the sensors read in step S201. The targetacceleration is set mainly based on the amount of depression of theaccelerator pedal (not illustrated) detected by the accelerator positionsensor 44 (FIG. 5 ). In other words, when the driver depresses theaccelerator pedal, the target acceleration is set high and the requestedoutput power becomes high, and the requested output power when theamount of depression of the accelerator pedal is large is set higherthan the requested output power when the amount of depression of theaccelerator pedal is small. In contrast, when the driver depresses thebrake pedal (not illustrated) with the intention of decelerating thevehicle 1, the target acceleration is set to a negative value (thetarget deceleration is set). The target deceleration (negative targetacceleration) is set mainly based on the amount of depression of thebrake pedal detected by the brake sensor 46 (FIG. 5 ).

Next, in step S203, it is determined whether the target acceleration setin step S202 is zero or more. The processing proceeds to step S204 whenthe target acceleration is zero or more (accelerates or travels at aconstant speed) or the processing proceeds to step S208 when the targetacceleration is less than zero (deceleration). Since the driver hasstarted the vehicle 1 and the vehicle 1 is accelerating at time t₂₀₁ inFIG. 14 , the processing of the flowchart proceeds to step S204.

Furthermore, in step S204, it is determined whether the motor outputpower (requested output power of the driver) required to achieve thetarget acceleration set in step S202 is equal to or more than thepredetermined output power. The processing proceeds to step S207 whenthe motor output power is less than the predetermined output power orthe processing proceeds to step S205 when the motor output power isequal to or more than the predetermined output power. Since the driverhas just started the vehicle 1 and the vehicle speed is still lowimmediately after time t₂₀₁ in FIG. 14 , the requested output power issmall and the processing of the flowchart proceeds to step S207.

The requested output power is calculated mainly based on the acceleratorposition (the amount of depression of the accelerator pedal) and thevehicle speed and the requested output power becomes relatively smallwhen the vehicle speed is low. Although the requested output power isestimated based on the vehicle speed and the processing is switched inthe first embodiment described above, the processing is directlyswitched based on the requested output power in the embodiment. In theembodiment, step S205 is executed when the motor output power requiredto achieve the target acceleration is 25 kW or more.

In step S207, the control parameter for the main drive motor 16 is setso that the target acceleration can be obtained by the driving force ofthe main drive motor 16. In contrast, in step S207, the controlparameter for the auxiliary drive motors 20 is set as to stop the motors(no driving force is generated and no kinetic energy is regenerated).Next, the processing proceeds to step S206, the control parameter set instep S207 is sent from the control device 24 to the main drive motor 16and the auxiliary drive motors 20, and the processing of the flowchartin FIG. 13 is completed once. By receiving the control parameter in stepS206, the main drive motor 16 generates a torque, increases the vehiclespeed, and achieves the target acceleration (from time t₂₀₁ to time t₂₀₂in FIG. 14 ).

In the example illustrated in FIG. 14 , the vehicle 1 is acceleratedfrom time t₂₀₁ to time t₂₀₂. In this period, the processing of stepsS201, S202, S203, S204, S207, and S206 in the flowchart in FIG. 13 isrepeatedly executed.

Next, when the driver releases the accelerator pedal at time t₂₀₂ inFIG. 14 , the target acceleration to be set in step S202 in FIG. 13becomes zero (constant speed travel). Also in this state, the processingof the flowchart in FIG. 13 proceeds to step S204 and then step 207 fromstep S203. In this state, in step S207, the control parameter for themain drive motor 16 is set so that a constant speed travel is maintainedby the driving force of the main drive motor 16. That is, the controlparameter is set so that the main drive motor 16 generates a drivingforce corresponding to the travel resistance of the vehicle 1 andmaintains a constant speed. Accordingly, the driving force generated bythe main drive motor 16 becomes smaller than the driving force duringacceleration of the vehicle 1. In contrast, in step S207, the controlparameter for the auxiliary drive motors 20 is set so as to stop themotors. Next, the processing proceeds to step S206, the controlparameters set in step S207 are sent to the individual motors, and theprocessing of the flowchart in FIG. 13 is completed once.

In the example illustrated in FIG. 14 , the vehicle 1 travels at aconstant speed from time t₂₀₂ to time t₂₀₃. In this period, theprocessing of steps S201, S202, S203, S204, S207, and S206 in theflowchart in FIG. 13 is repeatedly executed.

Next, when the driver depresses the accelerator pedal again at time t₂₀₃in FIG. 14 , the target acceleration to be set in step S202 in FIG. 13becomes a positive value. Still in this state, in step S207 in FIG. 13 ,the control parameter for the main drive motor 16 is set so that the settarget acceleration is achieved and the control parameter for theauxiliary drive motors 20 is set so as to stop the motors. In theexample illustrated in FIG. 14 , the vehicle 1 travels at a constantacceleration from time t₂₀₃ to time t₂₀₄ and the speed thereofincreases.

Next, when the driver further depresses the accelerator pedal at timet₂₀₄ and it is determined in step S204 that the requested output poweris equal to or more than predetermined output power (for example, 25kW), the processing of the flowchart in FIG. 13 proceeds to step S205from step S204. In step S205, the control parameters for the main drivemotor 16 and the auxiliary drive motors 20 are set so that the targetacceleration can be obtained by the driving forces of the main drivemotor 16 and the auxiliary drive motors 20. That is, the controlparameters are set so that the sum of the output power of the main drivemotor 16 and the output power of the auxiliary drive motors 20 equalsthe requested output power.

As described above, in the embodiment, the control device 24 causes themain drive motor 16 to generate a driving force and the auxiliary drivemotors 20 not to generate driving forces when the requested output powerof the driver is less than the predetermined output power. When therequested output power of the driver is equal to or more than thepredetermined output power, the control device 24 causes the main drivemotor 16 and the auxiliary drive motors 20 to generate driving forces.That is, the target acceleration set in step S202 is achieved by thedriving forces generated by the main drive motor 16 and the auxiliarydrive motors 20. In the example illustrated in FIG. 14 , when the driverdepresses the accelerator pedal, the target acceleration increases, therequested output power exceeds the predetermined output power, and theauxiliary drive motors 20 also generate driving forces. However, sincethe requested output power also increases due to an increase in thevehicle speed, the driving by the auxiliary drive motors 20 may startbecause the requested output power exceeds the predetermined outputpower when the vehicles travels at a certain target acceleration.

In the example illustrated in FIG. 14 , the vehicle 1 travels at aconstant acceleration from time t₂₀₄ to time t₂₀₅ and the speed thereofincreases. In this period, the processing of steps S201, S202, S203,S204, S205, and S206 in the flowchart in FIG. 13 is repeatedly executed.

Next, when the driver releases the accelerator pedal at time t₂₀₅ inFIG. 14 , the target acceleration to be set in step S202 in FIG. 13becomes zero (constant speed travel). This causes the processing of theflowchart in FIG. 13 to proceed to step S207 from step S204 again andthe processing of steps S201, S202, S203, S204, S207, and S206 isrepeatedly executed. In step S207, the control parameter for the maindrive motor 16 is set so that a constant speed travel is maintained bythe driving force of the main drive motor 16. Next, the processingproceeds to step S206, the control parameters set in step S207 are sentto the individual motors and the processing of the flowchart in FIG. 13is completed once. It should be noted here that the present inventionmay be configured so that a constant speed travel is maintained only bythe driving forces of the auxiliary drive motors 20 during a high speedtravel.

Next, when the driver operates the brake pedal (not illustrated) of thevehicle 1 at time t₂₀₆ in FIG. 14 , the target acceleration to be set instep S202 of the flowchart in FIG. 13 becomes a negative value (targetdeceleration). This causes the processing of the flowchart to proceed tostep S208 from step S203.

In step S208, it is determined whether the vehicle speed detected by thevehicle speed sensor 42 is equal to or more than the predeterminedsecond vehicle speed. Since the vehicle speed is high immediately aftertime t₂₀₆ in FIG. 14 , the processing of the flowchart proceeds to stepS210 from step S208. This causes the processing of steps S201. S202,S203, S208, S210, and S206 to be repeatedly executed. Although thepredetermined second vehicle speed is set to 100 km/h in the embodiment,the predetermined second vehicle speed may be set to any vehicle speedequal to or more than 50 km/h.

In step S210, the control parameters for the main drive motor 16 and theauxiliary drive motors 20 are set so that these motors regenerate thekinetic energy of the vehicle 1. Furthermore, when the set controlparameters are sent to the main drive motor 16 and the auxiliary drivemotors 20 in step S206, the kinetic energy is regenerated by thesemotors.

When the vehicle speed is reduced by an operation of the brake pedal(not illustrated) by the driver and the speed of the vehicle 1 becomesless than the predetermined second vehicle speed (100 km/h in theembodiment) at time t₂₀₇ in FIG. 14 , the processing of the flowchartproceeds to step S209 from step S208 and the processing of steps S201,S202, S203, S209, and S206 is repeatedly executed. In step S209, thecontrol parameters for the main drive motor 16 and the auxiliary drivemotors 20 are set so that the main drive motor 16 stops (no drivingforce is generated and no kinetic energy is regenerated) and theauxiliary drive motors 20 regenerate the kinetic energy of the vehicle1. In addition, when the set control parameters are sent to the maindrive motor 16 and the auxiliary drive motors 20 in step S206, thekinetic energy is regenerated by the auxiliary drive motors 20. Thisreduces the vehicle speed and the vehicle 1 stops at time t₂₀₈ in FIG.14 .

In the vehicle drive device according to the second embodiment of thepresent invention, since the main drive motor 16, which is the body sidemotor, and the in-while motors, which are the auxiliary drive motors 20,generate driving forces (step S205 in FIG. 13 ) when the requestedoutput power of the driver is equal to or more than the predeterminedoutput power (from step S204 to step S205 in FIG. 13 ), the in-wheelmotors are not requested for large output power. As a result, sincesmall motors with small output power may be adopted as the in-wheelmotors, the vehicle can be efficiently driven using the in-wheel motors.It should be noted here that the vehicle drive device according to thefirst embodiment of the present invention has the same effect.

In the vehicle drive device according to the embodiment, since therequested output power of the driver is set based on the amount ofdepression of the accelerator pedal detected by the accelerator positionsensor 44 (steps S201 and S202 in FIG. 13 ) and the requested outputpower of the driver is set to a large value when the amount ofdepression of the accelerator pedal is large, the intention of thedriver can be more accurately reflected in the requested output power.

The vehicle drive devices according to the first and second embodimentsof the present invention have been described above. Although the vehicledrive device according to the present invention is applied to an FR(front engine/rear drive) vehicle in any of the first and secondembodiments described above, the present invention is also applicable tovarious types of vehicles such as a so-called FF (front engine/frontdrive) vehicle in which an engine and/or a main drive motor are disposedin the front portion of the vehicle and the front wheels are the maindrive wheels or a so-called RR (rear engine/rear drive) vehicle in whichan engine and/or a main drive motor are disposed in the rear portion ofthe vehicle and the rear wheels are the main drive wheels.

When the present invention is applied to an FF vehicle, it is possibleto adopt a layout in which, for example, the engine 12, the main drivemotor 16, and the transmission 14 c are disposed in the front portion ofa vehicle 101 and front wheels 102 a are driven as the main drivewheels, as illustrated in FIG. 15 . In addition, the auxiliary drivemotors 20 can be disposed as in-wheel motors in the left and right rearwheels 102 b, which are the auxiliary drive wheels. As described above,the present invention can be configured so that the main drive motor 16,which is the body side motor, drives the front wheels 102 a, which arethe main drive wheels, and the auxiliary drive motors 20, which are thein-wheel motors, drive the rear wheels 102 b, which are the auxiliarydrive wheels. In this layout, the main drive motor 16 can be driven bythe electric power supplied via the inverter 16 a and stored in thebattery 18. In addition, an integrated unit formed by integrating thecapacitor 22, the high voltage DC/DC converter 26 a and the low voltageDC/DC converter 26 b, which are voltage converting units, and the twoinverters 20 a can be disposed in the rear portion of the vehicle 101.Furthermore, the auxiliary drive motors 20 can be driven by the electricpower supplied via the inverters 20 a and stored in the battery 18 andthe capacitor 22 that are disposed in series.

When the present invention is applied to an FF vehicle, it is possibleto adopt a layout in which, for example, the engine 12, the main drivemotor 16, and the transmission 14 c are disposed in the front portion ofa vehicle 201, and the front wheels 202 a are driven as the main drivewheels, as illustrated in FIG. 16 . In addition, the auxiliary drivemotors 20 can be disposed as in-wheel motors in the left and right frontwheels 202 a, which are the main drive wheels. As described above, thepresent invention can be configured so that the main drive motor 16,which is the body side motor, drives the front wheels 202 a, which arethe main drive wheels, and the auxiliary drive motors 20, which are thein-wheel motors, also drive the front wheels 202 a, which are the maindrive wheels. In this layout, the main drive motor 16 can be driven bythe electric power supplied via the inverter 16 a and stored in thebattery 18. In addition, an integrated unit formed by integrating thecapacitor 22, the high voltage DC/DC converter 26 a and the low voltageDC/DC converter 26 b, which are voltage converting units, and the twoinverters 20 a can be disposed in the rear portion of the vehicle 201.Furthermore, the auxiliary drive motors 20 can be driven by the electricpower supplied via the inverters 20 a and stored in the battery 18 andthe capacitor 22 that are disposed in series.

In contrast, when the present invention is applied to an FR vehicle, itis possible to adopt a layout in which, for example, the engine 12 andthe main drive motor 16 are disposed in the front portion of a vehicle301 and rear wheels 302 b are driven as the main drive wheels by leadingelectric power to the rear portion of the vehicle 301 via the propellershaft 14 a, as illustrated in FIG. 17 . The rear wheels 302 b are drivenby the power led to the rear portion by the propeller shaft 14 a via theclutch 14 b and the transmission 14 c, which is a stepped transmission.In addition, the auxiliary drive motors 20 can be disposed as in-wheelmotors in the left and right rear wheels 302 b, which are the main drivewheels. As described above, the present invention can be configured sothat the main drive motor 16, which is the body side motor, drives therear wheels 302 b, which are the main drive wheels, and the auxiliarydrive motors 20, which are the in-wheel motors, also drive the rearwheels 302 b, which are the main drive wheels. In this layout, the maindrive motor 16 can be driven by the electric power supplied via theinverter 16 a and stored in the battery 18. In addition, an integratedunit formed by integrating the capacitor 22, the high voltage DC/DCconverter 26 a and the low voltage DC/DC converter 26 b, which arevoltage converting units, and the two inverters 20 a can be disposed inthe front portion of the vehicle 301. Furthermore, the auxiliary drivemotors 20 can be driven by the electric power supplied via the inverters20 a and stored in the battery 18 and the capacitor 22 that are disposedin series.

Although preferred embodiments of the present invention have beendescribed above, various modifications can be made to the embodimentsdescribed above. In particular, the present invention is applied to ahybrid drive device including an engine and a motor in the embodimentsdescribed above, but the present invention is applicable to a vehicledrive device that drives a vehicle only by a motor without having anengine.

REFERENCE SIGNS LIST

-   -   1: vehicle    -   2 a: rear wheel (main drive wheel)    -   2 b: front wheel (auxiliary drive wheel)    -   4 a: subframe    -   4 b: front side frame    -   4 c: dash panel    -   4 d: propeller shaft tunnel    -   6 a: engine mount    -   6 b: capacitor mount    -   8 a: upper arm    -   8 b: lower arm    -   8 c: spring    -   8 d: shock absorber    -   10: hybrid drive device (vehicle drive device)    -   12: engine (internal combustion engine)    -   14: power transmission mechanism    -   14 a: propeller shaft    -   14 b: clutch    -   14 c: transmission (stepped transmission, automatic        transmission)    -   14 d: torque tube    -   16: main drive motor (main drive electric motor, body side        motor)    -   16 a: inverter    -   18: battery (electric storage unit)    -   20: auxiliary drive motor (auxiliary drive electric motor,        in-wheel motor)    -   20 a inverter    -   22: capacitor    -   22 a: bracket    -   22 b: harness    -   24: control device (controller)    -   25: electrical component    -   26 a: high voltage DC/DC converter (voltage converting unit)    -   26 b: low voltage DC/DC converter    -   28: stator    -   28 a: stator base    -   28 b: stator shaft    -   28 c: stator coil    -   30: rotor    -   30 a: rotor body    -   30 b: rotor coil    -   32: electrical insulating liquid chamber    -   32 a: electrical insulating liquid    -   34: bearing    -   40: mode selection switch    -   42: vehicle speed sensor    -   44: accelerator position sensor    -   46: brake sensor    -   48: engine RPM sensor    -   50: automatic transmission input rotation sensor    -   52: automatic transmission output rotation sensor    -   54: voltage sensor    -   56: current sensor    -   58: fuel injection valve    -   60: spark plug    -   62: hydraulic solenoid valve    -   101: vehicle    -   102 a: front wheel (main drive wheel)    -   102 b: rear wheel (auxiliary drive wheel)    -   201: vehicle    -   202 a: front wheel (main drive wheel)    -   301: vehicle    -   302 b: rear wheel (main drive wheel)

The invention claimed is:
 1. A vehicle drive device comprising: anin-wheel motor provided in a wheel of a vehicle, the wheel being locatedoutside of a body of the vehicle, the in-wheel motor configured to drivethe wheel; a body side motor provided in the body of the vehicle andconfigured to drive the wheel of the vehicle or another wheel of thevehicle via a drive shaft that is connected to a combustion engine ofthe vehicle; and a controller that controls the in-wheel motor and thebody side motor, wherein the controller is configured to: determinewhether or not a target acceleration is greater than or equal to zero;upon determining that the target acceleration is greater than or equalto zero: when a requested output power of the driver is less than apredetermined output power, control the body side motor to generate abody side motor driving force and the in-wheel motor not to generate anin-wheel motor driving force, and when the requested output power of thedriver is equal to or more than the predetermined output power, controlthe body side motor to generate the body side motor driving force andthe in-wheel motor to generate the in-wheel motor driving force; andupon determining that the target acceleration is less than zero: when aspeed of the vehicle is less than a predetermined speed threshold,control the body side motor not to generate a body side motorregenerative energy and the in-wheel motor to generate an in-wheel motorregenerative energy, and when the speed of the vehicle is equal to orgreater than the predetermined speed threshold, control the body sidemotor to generate the body side motor regenerative energy and thein-wheel motor to generate the in-wheel motor regenerative energy. 2.The vehicle drive device according to claim 1, further comprising: anaccelerator position sensor that detects an amount of depression of anaccelerator pedal of the vehicle, wherein the controller sets therequested output power of the driver based on the amount of depressionof the accelerator pedal detected by the accelerator position sensor,and when the amount of depression of the accelerator pedal is largerthan an accelerator depression threshold, the requested output power ofthe driver is set to a first output power that is larger than a secondoutput power corresponding to when the amount of depression of theaccelerator pedal is smaller than the accelerator depression threshold;and a brake position sensor that detects a depression of a brake pedalof the vehicle, wherein the controller sets the target acceleration tobe less than zero based on the depression of the accelerator pedaldetected by the brake position sensor.
 3. The vehicle drive deviceaccording to claim 1, wherein the in-wheel motor is an induction motor.4. The vehicle drive device according to claim 1, wherein the body sidemotor is a permanent magnet motor.
 5. The vehicle drive device accordingto claim 1, wherein the wheel driven by the in-wheel motor is a frontwheel of the vehicle and the wheel driven by the body side motor is arear wheel of the vehicle.
 6. The vehicle drive device according toclaim 1, wherein the wheel driven by the in-wheel motor is a rear wheelof the vehicle and the wheel driven by the body side motor is a frontwheel of the vehicle.
 7. The vehicle drive device according to claim 1,wherein the wheel driven by the in-wheel motor and the body side motoris a front wheel of the vehicle.
 8. The vehicle drive device accordingto claim 1, wherein the wheel driven by the in-wheel motor and the bodyside motor is a rear wheel of the vehicle.